I think it's to show the tone of the post. If you are texting a friend and just say I'm at the supermarket. It seems a bit off but if you said I'm at the supermarket it's friendlier. I think it's hard to convey emotion online so people try to show emotions through emoticons and lols.

I don't like it. Toxic ex-friend used to use it as a P/A tool a lot of the time and now whenever I see it I just think it's incredibly naff, possibly a bit thick and sometimes hiding some other meaning.

I thought that with the introduction of the emoji, the humble LOL was dying out. There's been an actual survey done and evryfing, innit. I think the actual meaning of LOL had been lost somewhere down the line though.